Question

The average age of 80 boys in a class is 15 yr. The average age of a group of 15 boys in the class is 16 yr and the average age of another 25 boys in the class is 14 yr. What is the average age of the remaining boys in the class?

• A. 15.25 yr
• B. 14 yr
• C. 14.75 yr
• D. Cannot be determined
• E. None of these

Answer 1

The correct option is A 15.25 yr

Let the required average age of the remaining boys be 'x'.
Now, according to the question,
80 $\times$ 15 = 15 $\times$ 16 + 25 $\times$ 14 + 40 $\times$ x
$\Rightarrow$ 1200 = 240 + 350 + 40x
$\Rightarrow$ 40x = 1200 - 240 - 350
$\Rightarrow$ 40x = 610
$\Rightarrow$ $x=\frac{610}{40}=15.25yr$